Various biological testing procedures require thermal cycling, generally to cause a chemical reaction via heat exchange. One example of such a procedure is polymerase chain reaction (PCR) for DNA amplification. Further examples include isothermal nucleic acid amplification, rapid-PCR, ligase chain reaction (LCR), self-sustained sequence replication, enzyme kinetic studies, homogeneous ligand binding assays, and more complex biochemical mechanistic studies that require complex temperature changes.
Such procedures require a testing system that can accurately raise and lower sample temperatures with precision, and in some cases rapidity. Many such systems exist, which typically use cooling devices (e.g., fans) that occupy a large amount physical space and require significant power to provide a required amount of performance (i.e., a rapid temperature drop). Further, such cooling devices have issues with start-up lag time and shut-down overlap, that is, will function after being shut off, and thus do not operate with instantaneous digital-like precision. For example, a centrifugal fan will not instantly blow at full volumetric capability when turned on and will also continue to rotate after power is shut off, thus implementing overlap time that must be accounted for in testing. Such issues typically get worse with device age.
The low cost of such cooling devices, relatively acceptable performance, and easy implementation has prevented industry from answering these issues. The answer thus far, has been to incorporate more powerful fans having greater volumetric output rates, which also increase space and power requirements. One price of this is a negative effect on portability of field testing systems, which can be used, for example, to rapidly detect viral outbreaks in outlying areas. Accordingly, there is an unanswered need to address the deficiencies of known cooling devices used in biological testing systems.